Use of comb polymers for controlling the rheology of mineral binder compositions

ABSTRACT

A comb polymer is used for increasing the flow rate and/or reducing the viscosity of a mineral binder composition, where the comb polymer has a main chain including acid groups and there are pendent chains linked to the main chain, and where the average number-average molar mass of all of the pendent chains is from 120 to 1000 g/mol and the molar ratio of the acid groups to the side chains is in the range from 0.5 to 2.

TECHNICAL FIELD

The invention relates to the use of a comb polymer for increasing theflow rate and/or for reducing the viscosity of a mineral bindercomposition. A further aspect of the invention relates to a mineralbinder composition and also to a cured molding comprising the combpolymer.

PRIOR ART

Dispersants or flow agents are used in the construction industry asplasticizers or water reducers for binder compositions, such asconcrete, mortars, cements, plasters, and lime, for example. Thedispersants are generally organic polymers, which are added to themixing water or admixed in solid form to the binder compositions. As aresult it is possible advantageously to modify not only the bindercomposition consistency during processing but also the properties in thecured state.

The selection and level of addition of a suitable dispersant aredependent in particular on the specific composition, the processingtechnology or the intended use of the binder composition. This is ademanding task particularly in the case of special binder compositions,such as specialty concretes or specialty mortars, for example.

The specialty concretes include, for example, what is called“self-compacting concrete” (SCC). Self-compacting concrete has a uniqueflow capacity and inherent compaction behavior. Accordingly,self-compacting concrete flows rapidly and without separation, purely onthe basis of gravity, automatically fills cavities, and is deaeratedwithout application of compaction energy. Vibrating as in the case ofconventional concrete is therefore unnecessary. Self-compacting concreteis therefore particularly advantageous when high laying capacity isrequired, with demanding geometric shapes, with narrow-meshreinforcement, with relatively thin components, or in situations whereapplication of additional compaction energy is difficult or evenimpossible. In comparison to customary concrete, self-compactingconcrete typically exhibits a modified grading curve and/or a higherlevel of fine-grain material.

With self-compacting concrete, optimum processing properties areachieved only if both the yield point or the slump flow and theviscosity or the flow rate of the concrete are each set within definedranges at the same time. Otherwise there may easily be separation ordemixing of the concrete constituents; inadequate flow behavior orstagnation may result, or unwanted air inclusions occur.

The selection of a suitable dispersant and the level of addition thereofin self-compacting concrete is therefore not trivial. Used customarilyin the art are high-performance plasticizers in the form ofpolycarboxylate ethers.

In this context, WO 2009/044046 discloses, for example, dispersantsbased on polycarboxylate-based comb polymers which can be used amongother things to reduce the viscosity of self-leveling bindercompositions. These comb polymers have especially hydrophobic groups inthe side chains.

Many of the known dispersants, however, are unable to provide completesatisfaction. On the one hand, known dispersants frequently influenceboth the slump flow and the flow rate of the mineral binder compositionat the same time. A targeted increase in the flow rate of the mineralbinder composition, without alteration to the yield point or the slumpflow, is therefore almost impossible. Other dispersants call for specialchemical groups or complicated chemical structures, which in turncomplicates production and renders it expensive.

Consequently there continues to be a demand for improved dispersants,which do not have the disadvantages stated.

DESCRIPTION OF THE INVENTION

It is an object of the present invention, therefore, to provide adispersant which permits a targeted increase in the flow rate and/or areduction in the viscosity of mineral binder compositions. As far aspossible, other properties of the mineral binder compositions, moreparticularly the slump flow or the yield point, are to remain unaltered.Preferably, moreover, the dispersant is to be suitable for use withother additives. The dispersant is intended in particular to be suitablefor self-compacting concrete.

Surprisingly it has been found that the object is achieved by thefeatures of independent claim 1.

The core of the invention lies in the use of a comb polymer forincreasing the flow rate and/or for reducing the viscosity of a mineralbinder composition, the comb polymer having a main chain comprising acidgroups, and side chains being attached on the main chain, with thenumber-average molecular weight (M_(n)) of all side chains being120-1000 g/mol, and with the molar ratio of the acid groups to the sidechains being in the range of 0.5-2.

As has emerged, it is possible when using the comb polymers of theinvention to obtain mineral binder compositions, in the form ofself-compacting concrete, for example, with greatly improved fillabilityand flow rate. This is achievable without significant separation ordemixing of the binder compositions, or air inclusions. Also surprising,in particular, is that the yield point of the binder compositions issubstantially unaffected by the comb polymers used, in spite of theincrease in the flow rate.

It has been found, moreover, that the comb polymers used in accordancewith the invention are highly compatible with other additives, such aswith further dispersants, for example.

Further aspects of the invention are subjects of further independentclaims. Particularly preferred embodiments of the invention are subjectsof the dependent claims.

WAYS OF PERFORMING THE INVENTION

A first aspect of the invention relates to the use of a comb polymer forincreasing the flow rate and/or for reducing the viscosity of a mineralbinder composition, the comb polymer having a main chain comprising acidgroups, and side chains being attached on the main chain, with thenumber-average molecular weight (M_(n)) of all side chains being120-1000 g/mol, and with a molar ratio of the acid groups to the sidechains being in the range of 0.5-2.

Contemplated presently as a measure of the flow rate is the t₅₀₀ timeaccording to DIN EN 12350-8:2010-12 (“Testing of fresh concrete—Part 8:Self-compacting concrete—Slump flow test”). The t₅₀₀ time is essentiallythe time in which the mixed or processable mineral binder compositionattains a slump flow of 500 mm (diameter). The shorter the t₅₀₀ time,the greater the flow rate.

In accordance with DIN EN 12350-8:2010-12, moreover, the flow rate is ameasure of the viscosity. The shorter the t₅₀₀ time, the higher the flowrate and the lower the viscosity of the mineral binder composition.

When the comb polymer is used in accordance with the invention, amineral binder composition mixed up with water exhibits an increasedflow rate and/or lower viscosity. This means that, following addition ofthe comb polymer of the invention, the composition flows more quickly orhas a lower viscosity in comparison with an analogous composition which,however, does not contain the comb polymer, or in comparison with ananalogous composition which comprises a comb polymer not of theinvention.

In the case of the inventive use and of a level of addition of 1 wt %,based on the binder content, the comb polymer preferably influences theyield point and/or the slump flow of the mineral binder composition,measured according to DIN EN 12350-8:2010-12, by less than 15%, moreparticularly less than 10%, preferably less than 5%, especially lessthan 2% or less than 1%. This means that the slump flow and/or the yieldpoint of the mineral binder composition, following addition of 1 wt % ofthe comb polymer of the invention, deviates by less than 15%, moreparticularly less than 10%, preferably less than 5%, especially lessthan 2% or less than 1%, from the slump flow of an analogous compositionwhich does not contain the comb polymer of the invention.

In accordance with the invention the number-average molecular weight(M_(r)) of the side chains is 120-1000 g/mol. In this context it ispossible for there to be not only side chains having a molecular weightin the range of 120-1000 g/mol but also side chains having a molecularweight of less than 120 g/mol and/or more than 1000 g/mol. On average,however, the number-average molecular weight (M_(n)) of all side chainsis always in the range of 120-1000 g/mol.

According to one advantageous embodiment, the maximum number-averagemolecular weight of the side chains is less than 1000 g/mol. In thiscase there are no side chains having a number-average molecular weightabove 1000 g/mol.

Preferably the number-average molecular weight (M_(n)) of the sidechains is in the range of 160-900 g/mol, preferably 250-800 g/mol, moreparticularly 300-750 g/mol, especially 400-600 g/mol or 450-550 g/mol.In that case an optimum increase in the flow rate is achieved and at thesame time the effect on the slump flow is minimized.

For specific applications, however, other molecular weights may also besuitable.

The weight-average molecular weight (M_(n)) and the number-averagemolecular weight (M_(n)) are determined presently by gel permeationchromatography (GPC) using polyethylene glycol (PEG) as a standard. Thistechnique is known per se to the person skilled in the art.

The molar ratio of the acid groups to the side chains is in particularin the range of 0.75-1.7, especially 0.8-1.6, more particularly 0.85-1.5or 0.9-1.2.

With advantage, the side chains are bonded to the main chain via ester,ether, amide and/or imide groups. Ester, ether and/or amide groups arepreferred, especially ester and/or ether groups.

More particularly the side chains comprise polyalkylene oxide sidechains. With preference at least 50 mol %, more particularly at least 75mol %, preferably at least 95 mol %, especially at least 98 mol % or 100mol % of the side chains consist of polyalkylene oxide side chains.

A fraction of ethylene oxide units in the polyalkylene oxide sidechains, based on all alkylene oxide units present in the side chains, ispreferably more than 90 mol %, more particularly more than 95 mol %,preferably more than 98 mol %, especially 100 mol %.

In particular the polyalkylene oxide side chains have no hydrophobicgroups, more particularly no alkylene oxides having three or more carbonatoms.

A high fraction of ethylene oxide units or a low level of alkyleneoxides having three or more carbon atoms reduces the risk of unwantedair entrainment.

The polyalkylene oxide side chains have, in particular, a structure inaccordance with formula -[AO]_(n)—R^(a). In this formula, in particular,A is C₂ to C₄ alkylene. R^(a) is preferably H or a C₁ to C₂₀ alkyl,cyclohexyl or alkylaryl group. Advantageously n is 2-250.

The term “acid groups” presently encompasses, in particular, carboxylgroups, sulfonic acid groups, phosphoric acid groups and/or phosphonicacid groups. The acid groups may each be in protonated form, indeprotonated form, for example as anion, and/or in the form of a saltwith a counterion or cation. Consequently, for example, the acid groupsmay be in partially or fully neutralized form.

The acid groups in particular have a structure according to formula—COOM, —SO₂—OM, —O—PO(OM)₂ and/or —PO(OM)₂. Very preferably the acidgroups have a structure according to the formula —COOM. Each M here,independently of the others, is H, an alkali metal ion, an alkalineearth metal ion, a di- or trivalent metal ion, an ammonium ion or anorganic ammonium group.

If M is an organic ammonium group, it derives in particular fromalkylamines or from C-hydroxylated amines, more particularly fromhydroxyalkylamines, such as ethanolamine, diethanolamine ortriethanolamine, for example.

A weight-average molecular weight (M_(w)) of the comb polymer is moreparticularly 5000-150 000 g/mol, preferably 10 000-100 000 g/mol. Anumber-average molecular weight (M_(n)) of the comb polymer isadvantageously 3000-100 000 g/mol, more particularly 8000-70 000 g/mol.

The comb polymer preferably comprises or consists of the followingstructural subunits:

-   -   a) a mole fractions of a structural subunit S1 of the formula        (I)

-   -   b) b mole fractions of a structural subunit S2 of the formula        (II)

-   -   c) optionally c mole fractions of a structural subunit S3 of the        formula (III)

-   -   d) optionally d mole fractions of a structural subunit S4 of the        formula (IV)

-   -   where    -   R¹, in each case independently of any other, is —COOM, —SO₂—OM,        —O—PO(OM)₂ and/or —PO(OM)₂,    -   R², R³, R⁵, R⁶, R⁹, R¹⁰, R¹³ and R¹⁴, in each case independently        of one another, are H or an alkyl group having 1 to 5 carbon        atoms,    -   R⁴, R⁷, R¹¹ and R¹⁵, in each case independently of one another,        are H, —COOM or an alkyl group having 1 to 5 carbon atoms,    -   M, independently of any other, is H⁺, an alkali metal ion, an        alkaline earth metal ion, a di- or trivalent metal ion, an        ammonium ion or an organic ammonium group,    -   m is 0, 1 or 2,    -   p is 0 or 1,    -   R⁸ and R¹², in each case independently of one another, are a C₁        to C₂₀ alkyl, cycloalkyl or alkylaryl group or are a group of        the formula -[AO]_(n)—R^(a),        -   where A is C₂ to C₄ alkylene, R^(a) is H, a C₁ to C₂₀ alkyl,            cyclohexyl or alkylaryl group,        -   and n is 2-250,    -   R¹⁶, independently of any other, is NH₂, —NR^(b)R^(c) or        —OR^(d)NR^(e)R^(f),        -   where R^(b) and R^(c), independently of one another, are            -   a C₁ to C₂₀ alkyl, cycloalkyl, alkylaryl or aryl group,            -   or are a hydroxyalkyl group or are an acetoxyethyl                (CH₃—CO—O—CH₂—CH₂—) or a hydroxyisopropyl                (HO—CH(CH₃)—CH₂—) or an acetoxyisopropyl                (CH₃—CO—O—CH(CH₃)—CH₂—) group;        -   or R^(b) and R^(c) together form a ring of which the            nitrogen is a part, in order to construct a morpholine or            imidazoline ring;        -   R^(d) is a C₂-C₄ alkylene group,        -   R^(e) and R^(f) each independently of one another are a C₁            to C₂₀ alkyl, cycloalkyl, alkylaryl or aryl group or a            hydroxyalkyl group,            and where a, b, c and d are mole fractions of the respective            structural subunits S1, S2, S3, and S4, where            a/b/c/d=(0.1-0.9)/(0.1-0.9)/(0-0.8)/(0-0.8), more            particularly a/b/c/d=(0.3-0.7)/(0.2-0.7)/(0-0.6)/(0-0.4),            preferably a/b/c/d=(0.4-0.7)/(0.3-0.6)/(0.001-0.005)/0, and            with the proviso that a+b+c+d is 1.

The sequence of the structural subunits S1, S2, S3, and S4 may bealternating, blocklike or random. It is also possible, moreover, forthere to be further structural subunits in addition to the structuralsubunits S1, S2, S3, and S4.

The structural subunits S1, S2, S3, and S4 together preferably have aweight fraction of at least 50 wt %, more particularly at least 90 wt %,very preferably at least 95 wt %, of the total weight of the combpolymer.

A ratio of a/(b+c+d)=is in particular in the range of 0.5-2, preferably0.75-1.7, especially 0.8-1.6, more particularly 0.85-1.5 or 0.9-1.2.

In the comb polymer, in particular, R¹ is COOM, R² is H or CH₃, andR³=R⁴=H. The comb polymer can therefore be prepared on the basis ofacrylic or methacrylic acid monomers, this being of advantage from aneconomic standpoint. With comb polymers of these kinds, moreover, aneffective reduction in viscosity is produced in the present context.

Likewise advantageous are comb polymers where R¹=COOM, R²=H, R³=H, andR⁴=COOM. Such comb polymers can be prepared on the basis of maleic acidmonomers.

Advantageously, R⁵ is H or CH₃ and R⁶=R⁷=H. Comb polymers of these kindscan be prepared, for example, starting from (meth)acrylic esters, vinylethers, (meth)allyl ethers or isoprenol ethers.

If S3 is present, then in particular R⁹ is H or CH₃ and R¹⁰=R¹¹=H.

If S4 is present, then in particular R¹³ is H or CH₃ and R¹⁴=R¹⁵=H.

Very advantageously, R² and R⁵ are mixtures of H and —CH₃. Preferred inthat case are mixtures with 40-60 mol % H and 40-60 mol % —CH₃. If thecorresponding structural subunits are present, this is also true, inparticular, for R⁹ and R¹³. With preference, moreover, R³ and R⁶ are H,and also, if the corresponding structural subunits are present, R⁹ andR¹³ are H.

According to a further advantageous embodiment, R¹ is COOM, R²=H,R⁵=—CH₃, and R³=R⁴=R⁶=R⁷=H.

In the case of another advantageous embodiment, R¹ is COOM, R²=R⁵=H or—CH₃, and R³=R⁴=R⁶=R⁷=H.

In particular, R⁸ and/or R¹² are -[AO]_(n)—R^(a), and preferably A is C₂alkylene and/or R^(a) is H or a C₁ alkyl group. Advantageously, n is2-30, more particularly n is 5-23, preferably n is 8-22, especially n is10-15.

In particular, m is 0 and p is 1. Likewise advantageously, m is 1 or 2and p is 0, and, in particular, R⁵ is —CH₃.

For particularly preferred comb polymers:

-   a) R¹ is COOM;-   b) R² and R⁵, independently of one another, are H, —CH₃ or mixtures    thereof. Very advantageously, R² and R⁵ are mixtures of H and —CH₃.    Preference in that case is given to mixtures with 40-60 mol % H and    40-60 mol % —CH₃. If structural subunits S3 and/or S4 are present,    this is also true, in particular, for R⁹ and R¹³;-   c) R³ and R⁶ are H. If structural subunits S3 and/or S4 are present,    this is also true, in particular, for R¹⁰ and/or R¹⁴;-   d) R⁴ and R⁷, independently of one another, are H or —COOM,    preferably H. If structural subunits S3 and/or S4 are present, this    is also true, in particular, for R¹¹ and R¹⁵;-   e) R⁸ is -[AO]_(n)—R^(a), and preferably A is C₂ alkylene and/or    R^(a) is H or a C₁ alkyl group. Advantageously n is 2-30, more    particularly n is 5-23, preferably n is 8-22, especially n is 10-15.    If structural subunit S3 is present, this is also true, in    particular, for R¹²;-   f) m is 0 and p is 1.

The mineral binder composition is more particularly a processable and/oraqueous mineral binder composition.

The mineral binder composition comprises at least one mineral binder.The expression “mineral binder” refers more particularly to a binderwhich reacts in the presence of water, in a hydration reaction, to givesolid hydrates or hydrate phases. This may be, for example, a hydraulicbinder (e.g., cement or hydraulic lime), a latent hydraulic binder(e.g., slag), a pozzolanic binder (e.g., flyash), or a nonhydraulicbinder (gypsum or white lime).

The mineral binder or the binder composition comprises more particularlya hydraulic binder, preferably cement. Particularly preferred is acement with a cement clinker fraction of ≦35 wt %. In particular thecement is of type CEM I, CEM II and/or CEM III, CEM IV or CEM V(according to standard EN 197-1). A fraction of the hydraulic binder asa proportion of the overall mineral binder is advantageously at least 5wt %, more particularly at least 20 wt %, preferably at least 35 wt %,especially at least 65 wt %. According to a further advantageousembodiment, the mineral binder consists to an extent of 95 wt % ofhydraulic binder, more particularly of cement clinker.

It may, however, also be advantageous if the mineral binder or themineral binder composition comprises or consists of other binders. Theseare, in particular, latent hydraulic binders and/or pozzolanic binders.Examples of suitable latent hydraulic and/or pozzolanic binders includeslag, flyash and/or silica dust. The binder composition may alsocomprise inert materials such as, for example, limestone, finely groundquartzes and/or pigments. In one advantageous embodiment the mineralbinder contains 5-95 wt %, more particularly 5-65 wt %, more preferably15-35 wt % of latent hydraulic and/or pozzolanic binders. Advantageouslatent hydraulic and/or pozzolanic binders are slag and/or flyash.

In one particularly preferred embodiment the mineral binder comprises ahydraulic binder, more particularly cement or cement clinker, and alatent hydraulic and/or pozzolanic binder, preferably slag and/orflyash. The fraction of the latent hydraulic and/or pozzolanic binder inthis case is more preferably 5-65 wt %, more preferably 15-35 wt %,while there is at least 35 wt %, especially at least 65 wt %, of thehydraulic binder.

The mineral binder composition is preferably a mortar composition orconcrete composition, more particularly self-compacting concrete. Themineral binder composition is more particularly a mineral bindercomposition which is processable and/or is mixed with water.

A weight ratio of water to binder in the mineral binder composition ispreferably in the range of 0.25-0.7, more particularly 0.26-0.65,preferably 0.27-0.60, especially 0.28-0.55.

The comb polymer is used advantageously with a fraction of 0.01-10 wt %,more particularly 0.1-7 wt % or 0.2-5 wt %, based on the binder content.

In particular, the mineral binder composition comprises fine-grainmaterial, preferably with a fraction>350 kg/m³, more particularly400-600 kg/m³. A cement content in this case is, in particular, between320 and 380 kg/m³.

The fine-grain material comprises, in particular, flyash, metakaolin,silica dust and/or inert, finely ground rock.

In particular the fine-grain material is as fine as cement. Inparticular the maximum particle diameter of the fine-grain material,measured by laser granulometry, for example, is below 0.125 mm.

The fine-grain material preferably has a Blaine fineness of at least1000 cm²/g, more particularly at least 1500 cm²/g, preferably at least2500 cm²/g, more preferably still at least 3500 cm²/g or at least 5000cm²/g.

In a further aspect, the invention relates to a composition, moreparticularly a mortar composition, a concrete composition or acementitious composition comprising at least one comb polymer asdescribed above and also a mineral binder. The mineral binder ispreferably a hydraulic binder, more particularly cement, preferablyPortland cement.

The composition is more particularly a self-compacting concretecomposition.

The comb polymer advantageously possesses a fraction of 0.01-10 wt %,more particularly 0.1-7 wt % or 0.2-5 wt %, based on the binder content.

More particularly the composition comprises fine-grain material,preferably with a fraction>350 kg/m³, more particularly 400-600 kg/m³.The cement content in this case is, in particular, between 320 and 380kg/m³.

A further aspect relates to a molding which is obtainable by curing acomposition as described above, more particularly a self-compactingconcrete, after addition of water.

The comb polymers used can be prepared in a conventional way.

A first process, also identified below as “polymer-analogous process”,for preparing a comb polymer as described above comprises the followingsteps:

-   -   a) providing and/or preparing a base polymer BP comprising or        consisting of a structural unit of the formula V

-   -   -   where        -   M, R¹, R², R³, and R⁴ are as defined above, with R¹ being            more particularly —COOM, and        -   m>2, more particularly m=20-100;

    -   b) esterifying the base polymer BP with a compound of the        formula VI

HO—R⁸  (VI)

-   -   c) optionally amidating the base polymer BP with a compound of        the formula VII

H₂N—R¹²  (VII)

-   -   d) optionally amidating and/or esterifying the base polymer BP        with a compound of the formula VIII

H—R¹⁶  (VIII)

-   -   -   to give the comb polymer CP,            where R⁸, R¹² and R¹⁶ are as defined above.

The base polymer BP in step a) is, in particular, a polyacrylic acid, apolymethacrylic acid and/or a copolymer of acrylic acid and methacrylicacid. A number-average molecular weight (M_(n)) of the base polymer BPof the formula (V) is, in particular, 500-20 000 g/mol, moreparticularly 500-10 000 g/mol, more preferably 3000-6000 g/mol.

Base polymers BP of this kind can be prepared in a conventional way fromacrylic acid monomers and/or methacrylic acid monomers. It is alsopossible, for example, to use maleic acid monomers and/or maleicanhydride monomers, however. This may be advantageous from standpointsincluding those of economy and safety.

The base polymer BP is prepared in step a), in particular by aqueousradical polymerization, of acrylic acid and/or methacrylic acid, forexample, in the presence of a radical initiator and/or of a chaintransfer agent.

The radical initiator in step a) comprises, in particular, Na—, K— orammonium peroxodisulfate. Likewise suitable as radical initiator in stepa) is, for example, a redox couple based on H₂O₂/Fe²⁺.

The chain transfer agent in step a) is preferably an alkali metalsulfite or hydrogen sulfite. Likewise advantageous is a phosphinic acidderivative. The chain transfer agent in step a) may also be an organiccompound which contains a thiol group.

Corresponding base polymers BP may in principle also be obtainedcommercially, from various suppliers.

Among the compounds which can be added for the esterification in step b)are acids and/or bases—as catalysts, for example. The esterificationtakes place advantageously at elevated temperatures of 120-200° C., moreparticularly 160-180° C. By this means it is possible to improve theyield significantly.

The compounds of the formulae V, VI and VII that are used in step b) areavailable commercially from various suppliers.

A second process, also identified below as “copolymerization process”,for preparing a comb polymer as described above comprises acopolymerization of:

-   -   a mole fractions of monomers M1 of the formula IX

-   -   b mole fractions of monomers M2 of the formula X

-   -   optionally c mole fractions of monomers M3 of the formula XI

-   -   optionally d mole fractions of monomers M4 of the formula XII

-   -   where a, b, c and d represent the mole fractions of the        respective monomers M1, M2, M3, and M4,    -   where a, b, c, d, M, R¹-R¹⁶, m, and p are as defined above.

The monomers M2, M3, and M4 may be prepared in a conventional way byesterification or amidation of acrylic acid, methacrylic acid, maleicacid and/or maleic anhydride with compounds of the formulae VI, VII orVIII (see above).

For the copolymerization or the second process it is possible to use theradical initiators and/or chain transfer agents already stated above inconnection with the first process.

WORKING EXAMPLES 1. Measurement Methods

Molecular weight determinations were made by gel permeationchromatography (GPC) with aqueous eluents. A closely calibratedpolyethylene glycol standard served for calibration. The eluent used wasa 0.1 M sodium nitrate solution with a pH of 12. The isocratic flow ratewas 0.8 ml/min. IGPC column: Varian Ultrahydrogel 7.8×300 mm. The peakswere quantified using a Varian RI-4 differential refractometer and aWaters SAT/IN module UV detector.

2. Materials Used

The starting materials used were as follows:

-   -   A polycarboxylic acid consisting of acrylic and methacrylic acid        units (molar ratio 1:1) was used. The polycarboxylic acid was        prepared by radical polymerization in accordance with known        preparation protocols. The average molar mass of the        polycarboxylic acid used is 5000 g/mol.    -   MPEG 500: Polyethylene glycol monomethyl ether with average        molar mass 500 g/mol. Ethylene oxide (EO) content: ˜11 EO        groups/mole.

3. Preparation Example for Comb Polymer

Comb polymer CP-1, consisting of structural subunits S1, S2, and S3 in amolar ratio of approximately 0.5/0.5/0.002, prepared bypolymer-analogous esterification of a polycarboxylic acid having a molarmass of about 5000 g/mol with MPEG 500. Degree of esterification: 50%,based on acid groups.

A 4-neck round-bottom flask with a capacity of 2 liters, fitted withmechanical stirrer, thermometer, gas inlet tube, and distillationbridge, was charged with 340 g of an aqueous solution of thepolycarboxylic acid (50 wt %). Subsequently, after heating had takenplace to 50° C., 500 g of MPEG 500 were added rapidly and the mixturewas heated to 165° C. over the course of 45 minutes under nitrogen, andmaintained at 165° C. for 30 minutes. Thereafter 4 g of 50% strengthaqueous sodium hydroxide solution were added and the temperature wasthen raised to 180° C., with simultaneous application of a reducedpressure of 80 mbar. This reaction solution was then maintained at 180°C. over the course of 4 hours, during which the internal pressure fellto 70 mbar.

After cooling had taken place to 90° C., 400 g of the melt wereconverted into a clear solution by being stirred into 400 g of water.Solids content: 49.9%

4. Fresh Concrete Tests 4.1 Production of a Reference Sample

A reference sample R1 was produced by dry-mixing Portland cement (CEM I,42.5; 325 kg/m³), slag (150 kg/m³), Sikafume (25 kg/m³), and aggregates(0-16 mm) in a mixer for 60 seconds. Then the mixing water (w/c=0.32),containing a conventional flow agent (2.5 wt %, based on binder content)in solution, was added, and the fresh concrete composition was mixedfurther mechanically for 3 minutes.

The conventional flow agent used is a polycarboxylate comb polymer withpolyethylene glycol side chains. The weight-average molecular weight ofthe side chains is approximately 2000 g/mol, and the molar ratio of theacid groups to the side chains is approximately 4.4.

4.2 Production of a Fresh Concrete Sample with Comb Polymer CP-1

The sample P1 was produced in the same way as for the reference sample.In addition to the conventional flow agent, however, 1 wt % (based onbinder content) of the comb polymer CP-1 was dissolved in the mixingwater, and admixed to the fresh concrete composition.

4.3 Fresh Concrete Properties

The flow behavior of fresh concrete compositions without (sample R1) andwith (sample P1) comb polymer CP-1 was determined in slump flow testsaccording to DIN EN 12350-8:2010-12 and also with a flow cup accordingto DIN EN 12350-9:2010-12, immediately after mixing had taken place.

Table 1 provides an overview of the results.

TABLE 1 Fresh concrete properties. Fraction of FA Fraction of t₅₀₀ Slumpflow Flow time No. [wt %] CP-1 [wt %] [s] [mm] [s] R1 2.5 0 21 720 >60P1 2.5 1 14 720 35

From the t₅₀₀ times and the flow times listed in Table 1 it is apparentin particular that the further addition of the comb polymer CP-1significantly reduces the viscosity of the fresh concrete compositionsand increases the flow rate. This is achieved, moreover, without anyeffect on the slump flow or yield point.

It is therefore possible to use CP-1 in a targeted way to control theviscosity or flow rate.

The embodiments described above are to be understood, however, merely asillustrative examples, which may be modified in any desired way withinthe bounds of the invention.

1. A comb polymer used for increasing the flow rate and/or for reducingthe viscosity of a mineral binder composition, the comb polymer having amain chain comprising acid groups, and side chains being attached on themain chain, with the number-average molecular weight (M_(n)) of all sidechains being 12 0-1000 g/mol, and with the molar ratio of the acidgroups to the side chains being in the range of 0.5-2.
 2. The combpolymer as claimed in claim 1, wherein the side chains are bonded to themain chain via ester, ether, amide and/or imide groups.
 3. The combpolymer as claimed in claim 1, wherein the number-average molecularweight (M_(n)) of the side chains is in the range of 250-800 g/mol. 4.The comb polymer as claimed in claim 1, wherein at least 50 mol % of theside chains consist of polyalkylene oxide side chains.
 5. The combpolymer as claimed in claim 4, wherein a fraction of ethylene oxideunits in the polyalkylene oxide side chains, based on all alkylene oxideunits present in the side chains, is more than 90 mol %.
 6. The combpolymer as claimed in claim 1, wherein the side chains have nohydrophobic groups.
 7. The comb polymer as claimed in claim 1, whereinin the comb polymer comprises or consists of the following structuralsubunits: a) a mole fractions of a structural subunit S1 of the formula(I)

b) b mole fractions of a structural subunit S2 of the formula (II)

c) optionally c mole fractions of a structural subunit S3 of the formula(III)

d) optionally d mole fractions of a structural subunit S4 of the formula(IV)

where R¹, in each case independently of any other, is —COOM, —SO₂—OM,—O—PO(OM)₂ and/or —PO(OM)₂, R², R³, R⁵, R⁶, R⁹, R¹⁰, R¹³ and R¹⁴, ineach case independently of one another, are H or an alkyl group having 1to 5 carbon atoms, R⁴, R⁷, R¹¹ and R¹⁵, in each case independently ofone another, are H, —COOM or an alkyl group having 1 to 5 carbon atoms,M, independently of any other, is H⁺, an alkali metal ion, an alkalineearth metal ion, a di- or trivalent metal ion, an ammonium ion or anorganic ammonium group, m is 0, 1 or 2, p is 0 or 1, R⁸ and R¹², in eachcase independently of one another, are a C₁ to C₂₀ alkyl, cycloalkyl oralkylaryl group or are a group of the formula -[AO]_(n)—R^(a), where Ais C₂ to C₄ alkylene, R^(a) is H, a C₁ to C₂₀ alkyl, cyclohexyl oralkylaryl group, and n is 2-250, R¹⁶, independently of any other, isNH₂, —NR^(b)R^(c) or —OR^(d)NR^(e)R^(f), where R^(b) and R^(c),independently of one another, are a C₁ to C₂₀ alkyl, cycloalkyl,alkylaryl or aryl group, or are a hydroxyalkyl group or are anacetoxyethyl (CH₃—CO—O—CH₂—CH₂—) or a hydroxyisopropyl (HO—CH(CH₃)—CH₂—)or an acetoxyisopropyl (CH₃—CO—O—CH(CH₃)—CH₂—) group; or R^(b) and R^(c)together form a ring of which the nitrogen is a part, in order toconstruct a morpholine or imidazoline ring; R^(d) is a C₂-C₄ alkylenegroup, R^(e) and R^(f) each independently of one another are a C₁ to C₂₀alkyl, cycloalkyl, alkylaryl or aryl group or a hydroxyalkyl group, andwhere a, b, c and d are mole fractions of the respective structuralsubunits S1, S2, S3, and S4, wherea/b/c/d=(0.1-0.9)/(0.1-0.9)/(0-0.8)/(0-0.8).
 8. The comb polymer asclaimed in claim 7, wherein R¹ is COOM; R² and R⁵, independently of oneanother, are H, —CH₃ or mixtures thereof; R³ and R⁶, independently ofone another, are H or CH₃; and R⁴ and R⁷, independently of one another,are H or COOM.
 9. The comb polymer as claimed in claim 7, wherein R⁸ is-[AO]_(n)—R^(a), A is C₂ alkylene, and R^(a) is H or a C₁ alkyl group,and where n is 2-30.
 10. The comb polymer as claimed in claim 7, whereinm is 0 and p is 1 and also R² and R⁵ are each mixtures of 40-60 mol % Hand 40-60 mol % —CH₃.
 11. The comb polymer as claimed in claim 1,wherein the comb polymer is used with a fraction of 0.01-10 wt % basedon the binder content.
 12. The comb polymer as claimed in claim 1,wherein the mineral binder composition is a mortar composition orconcrete composition.
 13. The comb polymer as claimed in claim 1,wherein the mineral binder composition comprises fine-grain material.14. A self-compacting concrete comprising at least one comb polymer asdescribed in claim
 1. 15. A molding obtainable by curing aself-compacting concrete as claimed in claim 14 after addition of water.